High speed, high density electrical connector

ABSTRACT

A high speed, high density electrical connector for use with printed circuit boards. The connector is in two pieces with one piece having pins and shield plates and the other having socket type signal contacts and shield plates. The shields have a grounding arrangement which is adapted to control the electromagnetic fields, for various system architectures, simultaneous switching configurations and signal speeds, allowing all of the socket type signal contacts to be used for signal transmission. Additionally, at least one piece of the connector is manufactured from wafers, with each ground plane and signal column injection molded into components which, when combined, form a wafer. This construction allows very close spacing between adjacent columns of signal contacts as well as tightly controlled spacing between the signal contacts and the shields. It also allows for easy and flexible manufacture, such as a connector that has wafers intermixed in a configuration to accommodate single ended, point to point and differential applications.

This invention relates generally to electrical connectors used tointerconnect printed circuit boards and more specifically to suchconnectors designed to carry many high speed signals.

Electrical connectors are used in many electronic systems. It isgenerally easier and more cost effective to manufacture a system onseveral printed circuit boards which are then joined together withelectrical connectors. A traditional arrangement for joining severalprinted circuit boards is to have one printed circuit board serve as abackplane. Other printed circuit boards, called daughter boards, areconnected through the backplane.

A traditional backplane is a printed circuit board with many connectors.Conducting traces in the printed circuit board connect to signal pins inthe connectors so that signals may be routed between the connectors.Other printed circuit boards, called "daughter boards" also containconnectors that are plugged into the connectors on the backplane. Inthis way, signals are routed among the daughter boards through thebackplane. The daughter cards often plug into the backplane at a rightangle. The connectors used for these applications contain a right anglebend and are often called "right angle connectors."

Connectors are also used in other configurations for interconnectingprinted circuit boards, and even for connecting cables to printedcircuit boards. Sometimes, one or more small printed circuit boards areconnected to another larger printed circuit board. The larger printedcircuit board is called a "mother board" and the printed circuit boardsplugged into it are called daughter boards. Also, boards of the samesize are sometimes aligned in parallel. Connectors used in theseapplications are sometimes called "stacking connectors" or "mezzanineconnectors."

Regardless of the exact application, electrical connector designs havegenerally needed to mirror trends in the electronics industry.Electronic systems generally have gotten smaller and faster. They alsohandle much more data than systems built just a few years ago. Thesetrends mean that electrical connectors must carry more and faster datasignals in a smaller space without degrading the signal.

Connectors can be made to carry more signals in less space by placingthe signal contacts in the connector closer together. Such connectorsare called "high density connectors." The difficulty with placing signalcontacts closer together is that there is electromagnetic couplingbetween the signal contacts. As the signal contacts are placed closertogether, the electromagnetic coupling increases. Electromagneticcoupling also increases as the speed of the signals increase.

In a conductor, the amount of electromagnetic coupling is indicated bymeasuring the "cross talk" of the connector. Cross talk is generallymeasured by placing a signal on one or more signal contacts andmeasuring the amount of signal coupled to another signal contact. Thechoice of which signal contacts are used for the cross talk measurementas well as the connections to the other signal contacts will influencethe numerical value of the cross talk measurement. However, any reliablemeasure of cross talk should show that the cross talk increases as thespeed of the signals increases and also as the signal contacts areplaced closer together.

A traditional method of reducing cross talk is to ground signal pinswithin the field of signal pins. The disadvantage of this approach isthat it reduces the effective signal density of the density of theconnector.

To make both a high speed and high density connector, connectordesigners have inserted shield members between signal contacts. Theshields reduce the electromagnetic coupling between signal contacts,thus countering the effect of closer spacing or higher frequencysignals. Shielding, if appropriately configured, can also control theimpedance of the signal paths through the connector, which can alsoimprove the integrity of signals carried by the connector.

An early use of shielding is shown in Japanese patent disclosure 49-6543by Fujitsu, Ltd. dated Feb. 15, 1974. U.S. Pat. Nos. 4,632,476 and4,806,107--both assigned to AT&T Bell Laboratories--show connectordesigns in which shields are used between columns of signal contacts.These patents describe connectors in which the shields run parallel tothe signal contacts through both the daughter board and the backplaneconnectors. Cantilevered beams are used to make electrical contactbetween the shield and the backplane connectors. U.S. Pat. Nos.5,433,617; 5,429,521; 5,429,520 and 5,433,618--all assigned to FramatomeConnectors International--show a similar arrangement. The electricalconnection between the backplane and shield is, however, made with aspring type contact.

Other connectors have the shield plate within only the daughter cardconnector. Examples of such connector designs can be found in U.S. Pat.Nos. 4,846,727; 4,975,084; 5,496,183; 5,066,236--all assigned to AMP,Inc. An other connector with shields only within the daughter boardconnector is shown in U.S. Pat. No. 5,484,310, assigned to Teradyne,Inc.

From the number of patents that describe connectors using shielding toreduce cross talk, it will be appreciated that the placement andconnection of the shields can have a great effect on the electricalperformance of the connector. The specific configuration of theshielding can also have a significant impact on the mechanicalproperties of the connector. For example, the manner in which theelectrical connection is made to the shield can influence whether thereis "stubbing" when the connectors are mated. Stubbing means that onecontact gets caught on another contact. When there is stubbing, one ofthe contacts is usually damaged, requiring that the connector berepaired or replaced.

It would be highly desirable to have a shield arrangement that is highlyeffective at reducing the cross talk between signal contacts. It wouldbe also highly desirable if the shielding arrangement were mechanicallyrobust. It would also be desirable if that connector were easy tomanufacture. It would further be highly desirable to control signalreflections by controlling the geometry of the shields and signalcontacts for impedance matching the connection.

SUMMARY OF THE INVENTION

With the foregoing background in mind, it is an object of the inventionto provide a high speed, high density connector.

It is a further object to provide a high performance connector thatallows all of its signal contacts to be used for carrying signals.

It is also an object to provide an electrical connector that ismechanically robust.

It is a further object to provide a connector that is easy tomanufacture.

The foregoing and other objects are achieved in an electrical connectorhaving shield plates between rows of signal contacts in both thedaughter board and backplane connectors. The shield plates in thebackplane connector have torsional contacts. The torsional contactssignificantly reduce the chance of stubbing. They also provide a highlydesirable pattern of current flow through the shields, which increasestheir effectiveness at reducing inductive coupling between signalcontacts and the resulting cross talk.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the followingmore detailed description and accompanying drawings in which

FIG. 1 is an exploded view of a connector made in accordance with theinvention;

FIG. 2 is a shield plate blank used in the connector of FIG. 1;

FIG. 3 is a view of the shield plate blank of FIG. 2 after it is insertmolded into a housing element;

FIG. 4 is a signal contact blank used in the connector of FIG. 1;

FIG. 5 is a view of the signal contact blank of FIG. 4 after it isinsert molded into a housing element;

FIG. 6 is an alternative embodiment of the signal contact blank of FIG.4 suitable for use in making a differential module;

FIGS. 7A-7C are operational views a prior art connector;

FIGS. 8A-8C are similar operational views of the connector of FIG. 1;

FIG. 9A and 9B are backplane hole and signal trace patterns for singleended and differential embodiments of the invention, respectively; and

FIG. 10 is a view of an alternative embodiment of the invention.

FIG. 11A is a an alternative embodiment for the plate 128 in FIG. 1;

FIG. 11B is a cross sectional view taken through the line B--B of FIG.11A;

FIG. 12 is an isometric view of a connector according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows an exploded view of backplane assembly 100. Backplane 110has pin header 114 attached to it. Daughter card 112 has daughter cardconnector 116 attached to it. Daughter card connector 116 can be matedto pin header 114 to form a connector. Backplane assembly likely hasmany other pin headers attached to it so that multiple daughter cardscan be connected to it. Additionally, multiple pin headers might bealigned end to end so that multiple pin headers are used to connect toone daughter card. However, for clarity, only a portion of backplaneassembly and a single daughter card 112 are shown.

Pin header 114 is formed from shroud 120. Shroud 120 is preferablyinjection molded from a plastic, polyester or other suitable insulativematerial. Shroud 120 serves as the base for pin header 114.

The floor (not numbered) of shroud 120 contains columns of holes 126.Pins 122 are inserted into holes 126 with their tails 124 extendingthrough the lower surface of shroud 120. Tails 124 are pressed intosignal holes 136. Holes 136 are plated through-holes in backplane 110and serve to electrically connect pins 122 to traces (not shown) onbackplane 110. For clarity of illustration, only a single pin 122 isshown. However, pin header 114 contains many parallel columns of pins.In a preferred embodiment, there are eight rows of pins in each column.

The spacing between each column of pins is not critical. However, it isone object of the invention to allow the pins to be placed closetogether so that a high density connector can be formed. By way ofexample, the pins within each column can be spaced apart by 2.25 mm andthe columns of pins can be spaced apart by 2 mm. Pins 122 could bestamped from 0.4 mm thick copper alloy.

Shroud 120 contains a groove 132 formed in its floor that runs parallelto the column of holes 126. Shroud 120 also has grooves 134 formed inits sidewalls. Shield plate 128 fits into grooves 132 and 134. Tails 130protrude through holes (not visible) in the bottom of groove 132. Tails130 engage ground holes 138 in backplane 110. Ground holes 138 areplated through-holes that connect to ground traces on backplane 110.

In the illustrated embodiment, plate 128 has seven tails 130. Each tail130 falls between two adjacent pins 122. It would be desirable forshield 128 to have a tail 130 as close as possible to each pin 122.However, centering the tails 130 between adjacent signal pins 122 allowsthe spacing between shield 128 and a column of signal pins 122 to bereduced.

Shield plate 128 has several torsional beams contacts 142 formedtherein. Each contact 142 is formed by stamping arms 144 and 146 inplate 128. Arms 144 and 146 are then bent out of the plane plate 128.Arms 144 and 146 are long enough that they will flex when pressed backinto the plane of plate 128. Arms 144 and 148 are sufficiently resilientto provide a spring force when pressed back into the plane of plate 128.The spring force generated by arms 144 and 146 creates a point ofcontact between each arm 144 or 146 and plate 150. The generated springforce must be sufficient to ensure this contact even after the daughtercard connector 116 has been repeatedly mated and unmated from pin header114.

During manufacture, arms 144 and 146 are coined. Coining reduces thethickness of the material and increases the compliancy of the beamswithout weakening of plate 128.

For enhanced electrical performance, it is desirable that arms 144 and146 be as short and straight as possible. Therefore, they are made onlyas long as needed to provide the required spring force. In addition, forelectrical performance, it is desirable that there be one arm 144 or 146as close as possible to each signal pin 122. Ideally, there would be onearm 144 and 146 for each signal pin 122. For the illustrated embodimentwith eight signal pins 122 per column, there would ideally be eight arms144 or 146, making a total of four balanced torsional beam contacts 142.However, only three balanced torsional beam contacts 142 are shown. Thisconfiguration represents a compromise between the required spring forceand desired electrical properties.

Grooves 140 on shroud 120 are for aligning daughter card connector 116with pin header 114. Tabs 152 fit into grooves 140 for alignment and toprevent side to side motion of daughter card connector 116 relative topin header 114.

Daughter card connector 116 is made of wafers 154. Only one wafer 154 isshown for clarity, but daughter card connector 116 has, in a preferredembodiment, several wafers stacked side to side. Each wafer 154 containsone column of receptacles 158. Each receptacle 158 engages one pin 122when the pin header 114 and daughter card connector 116 are mated. Thus,daughter card connector 116 is made from as many wafers as there arecolumns of pins in pin header 114.

Wafers 154 are supported in stiffener 156. Stiffener 156 is preferablystamped and formed from a metal strip. It is stamped with features tohold wafer 154 in a required position without rotation and thereforepreferably includes three attachment points. Stiffener 156 has slot 160Aformed along its front edge. Tab 160B fits into slot 160A. Stiffener 156also includes holes 162A and 164A. Hubs 162B and 164B fit into holes162A and 164A. The hubs 162B and 164B are sized to provide aninterference fit in holes 162A and 164A.

FIG. 1 shows only a few of the slots 160A and holes 162A and 164A forclarity. The pattern of slots and holes is repeated along the length ofstiffener 156 at each point where a wafer 156 is to be attached.

In the illustrated embodiment, wafer 154 is made in two pieces, shieldpiece 166 and signal piece 168. Shield piece 166 is formed by insertmolding housing 170 around the front portion of shield 150. Signal piece168 is made by insert molding housing 172 around contacts 410A . . .410H (FIG. 4).

Signal piece 168 and shield piece 166 have features which hold the twopieces together. Signal piece 168 has hubs 512 (FIG. 5) formed on onesurface. The hubs align with and are inserted into clips 174 cut intoshield 150. Clips 174 engage hubs 512 and hold plate 150 firmly againstsignal piece 168.

Housing 170 has cavities 176 formed in it. Each cavity 176 is shaped toreceive one of the receptacles 158. Each cavity 176 has platform 178 atits bottom. Platform 178 has a hole 180 formed through it. Hole 180receives a pin 122 when daughter card connector 116 mates with pinheader 114. Thus, pins 122 mate with receptacles 158, providing a signalpath through the connector.

Receptacles 158 are formed with two legs 182. Legs 182 fit on oppositesides of platform 178 when receptacles 158 are inserted into cavities176. Receptacles 158 are formed such that the spacing between legs 182is smaller than the width of platform 178. To insert receptacles 158into cavity 176, it is therefore necessary to use a tool to spread legs182.

The receptacles form what is known as a preloaded contact. Preloadedcontacts have traditionally been formed by pressing the receptacleagainst a pyramid shaped platform. The apex of the platform spreads thelegs as the receptacle is pushed down on it. Such a contact has a lowerinsertion force and is less likely to stub on the pin when the twoconnectors are mated. The receptacles of the invention provide the sameadvantages, but are achieved by inserting the receptacles from the siderather than by pressing them against a pyramid.

Housing 172 has grooves 184 formed in it. As described above, hubs 512(FIG. 5) project through plate 150. When two wafers are stacked side byside, hubs 512 from one wafer 154 will project into grooves 184 of anadjacent wafer. Hubs 512 and grooves 184 help hold adjacent waferstogether and prevent rotation of one wafer with respect to the next.These features, in conjunction with stiffener 156 obviate the need for aseparate box or housing to hold the wafers, thereby simplifying theconnector.

Housings 170 and 172 are shown with numerous holes (not numbered) inthem. These holes are not critical to the invention. They are "pinchholes" used to hold plates 150 or receptacle contacts 410 duringinjection molding. It is desirable to hold these pieces during injectionmolding to maintain uniform spacing between the plates and receptaclecontacts in the finished product.

FIG. 2 shows in greater detail the blank used to make plate 150. In apreferred embodiment, plates 150 are stamped from a roll of metal. Theplates are retained on carrier strip 210 for ease of handling. Afterplate 150 is injection molded into a shield piece 166, the carrier stripcan be cut off.

Plates 150 include holes 212. Holes 212 are filled with plastic fromhousing 170, thereby locking plate 150 in housing 170.

Plates 150 also include slots 214. Slots 214 are positioned to fallbetween receptacles 158. Slots 214 serve to control the capacitance ofplate 150, which can overall raise or lower the impedance of theconnector. They also channel current flow in the plate near receptacles158, which are the signal paths. Higher return current flow near thesignal paths reduces cross talk.

Slot 216 is similar to the slots 214, but is larger to allow a finger316 (FIG. 3) to pass through plate 150 when plate 150 is molded into ahousing 170. Finger 316 is a small finger of insulating material thatcould aid in holding a plate 128 against plate 150. Finger 316 isoptional and could be omitted. Note in FIG. 1 that the central twocavities 176 have their intermediate wall partially removed. Finger 316from an adjacent wafer 154 (not shown) would fit into this space tocomplete the wall between the two central cavities. Finger 316 wouldextend beyond housing 170 and would fit into a slot 184B of an adjacentwafer (not shown).

Slot 218 allows tail region 222 to be bent out of the plane of plate150, if desired. FIG. 9A shows traces 910 and 912 on a printed circuitboard routed between holes used to mount a connector according to theinvention. FIG. 9A shows portions of a column of signal holes 186 andportions of a column of ground contacts 188. When the connector is usedto carry single ended signals, it is desirable that the traces 910 and912 be separated by ground to the greatest extent possible. Thus, it isdesirable that the ground holes 188 be centered between the column ofsignal holes 186 so that the signal traces 910 and 912 can be routedbetween the signal holes 186 and ground holes 188. On the other hand,FIG. 9B shows the preferred routing for differential pair signals. Fordifferential pair signals, it is desirable that the traces be routed asclose together as possible. To allow the traces 914 and 916 to be closetogether, the ground holes 188 are not centered between columns ofsignal holes 186. Rather, they are offset to be as close to one row ofsignal contacts 186. That placement allows both signal traces 914 and916 to be routed between the ground holes 188 and a column of signalholes 186. In the single ended configuration, tail region 222 is bentout of the plane of plate 150. For the differential configuration, it isnot bent.

It should also be noted that plate 128 (FIG. 1) can be similarly bent inits tail region, if desired. In the preferred embodiment, though, plate128 is not bent for single ended signals and is bent for differentialsignals.

Tabs 220 are bent out of the plane of plate 150 prior to injectionmolding of the housing 170. Tabs 220 will wind up between holes 180(FIG. 1). Tabs 220 aid in assuring that plate 150 adheres to housing170. They also reinforce housing 170 across its face, i.e. that surfacefacing pin header 114.

FIG. 3 shows shield 150 after it has been insert molded into housing 170to form ground portion 166. FIG. 3 shows that housing 170 includespyramid shaped projections 310 on the face of shield piece 166. Matchingrecesses (not shown) are included in the floor of pin header 114.Projections 310 and the matching recesses serve to prevent the springforce of torsional beam contacts 142 from spreading adjacent wafers 154when daughter card connector 116 is inserted into pin header 114.

FIG. 4 shows receptacle contact blank 400. Receptacle contact blank ispreferably stamped from a sheet of metal. Numerous such blanks arestamped in a roll. In the preferred embodiment, there are eightreceptacle contacts 410A . . . 410H. The receptacle contacts 410 areheld together on carrier strips 412, 414, 416, 418 and 422. Thesecarrier strips are severed to separate contacts 410A . . . 410H afterhousing 172 has been molded around the contacts. The carrier strips canbe retained during much of the manufacturing operation for easy handlingof receptacle portions 168.

Each of the receptacle contacts 410A . . . 410H includes two legs 182.The legs 182 are folded and bent to form the receptacle 158.

Each receptacle contact 410A . . . 410H also includes a transmissionregion 424 and a tail region 426. FIG. 4 shows that the transmissionregions 424 are equally spaced. This arrangement is preferred for singleended signals as it results in maximum spacing between the contacts.

FIG. 4 shows that the tail regions are suitable for being press fit intoplated through-holes. Other types of tail regions might be used. Forexample, solder tails might be used instead.

FIG. 5 shows receptacle contact blank 400 after housing 172 has beenmolded around it.

FIG. 6 shows a receptacle contact blank 600 suitable for use in analternative embodiment of the invention. Receptacle contacts 610A . . .610H are grouped in pairs: (610A and 610B), (610C and 610D), (610E and610F) and (610G and 610H). Transmission regions 624 of each pair are asclose together as possible while maintaining differential impedance.This increases the spacing between adjacent pairs. This configurationimproves the signal integrity for differential signals.

The tail region 626 and the receptacles of receptacle contact blank 400and 600 are identical. These are the only portions of receptaclecontacts 410 and 610 extending from housing 172. Thus, externally,signal portion 168 is the same for either single ended or differentialsignals. This allows single ended and differential signal wafers to bemixed in a single daughter card connector.

FIG. 7A illustrates a prior art connector as an aid in explaining theimproved performance of the invention. FIG. 7A shows a shield plate 710with a cantilevered beam 712 formed in it. The cantilevered beam 712engages a blade 714 from the pin header. The point of contact is labeledX. Blade 714 is connected to a backplane (not shown) at point 722.

Signals are transmitted through signal pins 716 and 718 running adjacentto the shield plate. Plate 710 and blade 714 act as the signal return.The signal path 720 through these elements is shown as a loop. It shouldbe noted that signal path 720 cuts through pin 718. As is well known, asignal traveling in a loop passing through a conductor will inductivelycouple to the conductor. Thus, the arrangement of FIG. 7A will haverelatively high coupling or cross talk from pin 716 to 718.

FIG. 7B shows a side view of the arrangement of FIG. 7A. As thecantilevered beam 712 is above the blade 714 its distance from pin 716is d₁. In contrast, blade 714 has a spacing of d₂, which is larger. Inthe transmission of high frequency signals, the distance between thesignal path and the ground dictates the impedance of the signal path.Changes in distance mean changes in impedance. Changes in impedancecause signal reflections, which is undesirable.

FIG. 7C shows the same arrangement upon mating. The blade 714 must slideunder cantilevered beam 712. If not inserted correctly, blade 714 canbut up against the end of cantilevered beam 712. This phenomenon iscalled "stubbing." It is highly undesirable in a connector because itcan break the connector.

In contrast, FIG. 8 shows in a schematic sense the components of aconnector manufactured according to the invention. Shield plates 128 and150 overlap. Contact is made at the point marked X on torsional beam146. Signal path 820 is shown to pass through a signal pin 122, returnthrough plate 150 to point of contact X, pass through arm 146, throughplate 128 and through tail 130. Signal path 820 is then completedthrough the backplane (not shown in FIG. 8). Significantly, signal path820 does not cut through any adjacent signal pin 122. In this way, crosstalk is significantly reduced over the prior art.

FIG. 8B illustrates schematically plates 128 and 150 prior to mating ofdaughter card connector 116 to pin header 114. In the perspective ofFIG. 8B, arm 146 is shown bent out of the plane of plate 128. As plates150 and 128 slide along one another during mating, arm 146 is pressedback into the plane of plate 128.

FIG. 8C show plates 128 and 150 in the mated configuration. Dimple 810pressed into arm 146 is shown touching plate 150. The torsional springforce generated by pressing arm 146 back into the plane of plate 128ensures a good electrical contact. It should be noted that the spacingbetween the plates 128 or 150 and an adjacent signal contact do not haveas large a discontinuity as shown in FIG. 7B. This improvement shouldimprove the electrical performance of the connector.

It should also be noted that in moving from the configuration of FIG. 8Bto FIG. 8C, there is not an abrupt surface that could lead to stubbing.Thus, with torsional contacts, the mechanical robustness of theconnector should be improved in comparison to the prior art.

FIG. 10 shows an alternative embodiment of a wafer 154 (FIG. 1). In theembodiment of FIG. 10, a shield blank on carrier strip 1010 isencapsulated in an insulative housing 1070 through injection molding.Shield tails 1030 are shown extending from housing 1070. Housing 1070includes cavities 1016, 1017, 1018 and 1019. The shield blank is cut andbent to make contacts 1020 within cavities 1016, 1017, 1018 and 1019.

Cavities 1016, 1017, 1018 and 1019 have holes 1022 formed in theirfloors. Pins from the pin header are inserted through the holes duringmating and engage, through the springiness of the pin as well as ofcontacts 1020 ensure electrical connection to the shield.

In the embodiment of FIG. 10, the signal contacts are stampedseparately. The transmission line section of the contacts are laid intocavities 1026. The receptacle portions of the signal contacts areinserted into cavities 1024.

A wafer as in FIG. 10 illustrates that any number of signal contactsmight be used per column. In FIG. 10, four signal contacts per columnare shown. That figure also illustrates that pins might be used in placeof a plate 128. However, there might be differences in electricalperformance. A plate could be used in conjunction with the configurationof FIG. 10. In that case, instead of a series of separate holes 1022 incavities 1016, 1017, 1018 and 1019, a slot would be cut through thecavities.

FIG. 11A shows an alternative embodiment for contacts 142 on plate 128.Plate 1128 includes a series of torsional contacts 142. Each contact ismade by stamping an arm 1146 from plate 1128. Here the arms have agenerally serpentine shape. As described above, it is desirable for thearms 146 to be long enough to provide good flexibility. However, it isalso desirable for the current to flow through the contacts 1142 in anarea that is as narrow as possible in a direction perpendicular to theflow of current through signal pins 122. To achieve both of these goals,arms 1146 are stamped in a serpentine shape.

FIG. 11B shows plate 1128 in cross section through the line indicated asB--B in FIG. 1A. As shown, arms 1146 are bent out of the plane of plate1128. During mating of the connector half, they are pressed back intothe plane of plate 1128, thereby generating a torsional force.

FIG. 12 shows an additional view of connector 100. FIG. 12 shows face1210 of daughter card connector 116. The lower surface of pin header 114is also visible. In this view, it can be seen that the press fit tails124 of plate 128 have an orientation that is at right angles to theorientation of press fit tails 130 of signal pins 122.

EXAMPLE

A connector made according to the invention was made and tested. Thetest was made with the single ended configuration and measurements weremade on one signal line with the ten closest lines driven. For signalrise times of 500 ps, the backward crosstalk was 4.9%. The forward crosstalk was 3.2%. The reflection was too small to measure. The connectorprovided a real signal density of 101 per linear inch.

Having described one embodiment, numerous alternative embodiments orvariations might be made. For example, the size of the connector couldbe increased or decreased from what is shown. Also, it is possible thatmaterials other than those expressly mentioned could be used toconstruct the connector.

Various changes might be made to the specific structures. For example,clips 174 are shown generally to be radially symmetrical. It mightimprove the effectiveness of the shield plate 150 if clips 174 wereelongated with a major axis running parallel with the signal contacts insignal pieces 168 and a perpendicular minor axis which is as short aspossible.

Also, manufacturing techniques might be varied. For example, it isdescribed that daughter card connector 116 is formed by organizing aplurality of wafers onto a stiffener. It might be possible that anequivalent structure might be formed by inserting a plurality of shieldpieces and signal receptacles into a molded housing.

Therefore, the invention should be limited only by the spirit and scopeof the appended claims.

What is claimed is:
 1. An electrical connector comprising:a) a pinheader comprising:i) an insulative base; ii) a plurality of columns ofpins attached to the insulative based; iii) a first plurality ofconducting plates attached to the insulative base, each conducting platedisposed between an adjacent column of pins and each conducting platehaving formed therein a plurality of torsional contacts; b) a matingconnector piece comprising:i) an insulative base shaped to mate with theinsulative base of the pin header; ii) a plurality of columns ofreceptacles, each column having a plurality of receptacles disposed toengage one of the plurality of pins; iii) a second plurality ofconducting plates, each conducting plate disposed between an adjacentcolumn of receptacles and being disposed to engage the plurality oftorsional contacts on one of the plurality of conducting plates in thepin header.
 2. The electrical connector of claim 1 whereina) each of theplurality of columns of pins includes a first number of pins; and b)each of the first plurality of conducting plates in the pin header has asecond number of contact tails extending therefrom, said second numberbeing equal to or greater than the first number minus one.
 3. Theelectrical connector of claim 1 wherein each of the torsional contactscomprises at least one arm stamped from one of the first plurality ofconducting plates, the arm being connected to the plate at two pointsand bent out of the plane of the plate.
 4. The electrical connector ofclaim 1 wherein each of the torsional contacts comprises an arm stampedout of one of the first plurality of conducting plates, the arm having athickness less than the thickness of the conducting plate.
 5. Theelectrical connector of claim 1 wherein adjacent receptacles within thesame column are spaced apart by an amount less than or equal to 2 mm andadjacent columns of receptacles are spaced apart by an amount less thanor equal to 2.25 mm.
 6. The electrical connector of claim 1 wherein eachof the torsional contacts contains an arm and the arm has a serpentineshape.
 7. The electrical connector of claim 1 wherein the daughter cardconnector comprises a plurality of modules, the connector additionallycomprising a metal stiffener to which each of the plurality of modulesis attached.
 8. An electrical connector incorporated into a back planeassembly with a backplane and at least one daughter card, the electricalconnector comprising:a) a first connector piece having:i) a plurality ofpin shaped signal contacts, each signal contact having a tail portionattached to the backplane, the pin shaped signal contacts being disposedin a plurality of parallel columns; ii) a first plurality of shieldplates, each shield plate being disposed between adjacent columns ofsignal contacts and each having a plurality of tail portions extendingtherefrom and attached to the backplane, each tail portion of eachshield plate being disposed between tails portions of adjacent signalcontacts within the same column of signal contacts, wherein, for eachshield plate, there is one tail portion between each pair of adjacentsignal contacts in an adjacent column of signal contacts; b) a secondconnector piece having:i) a plurality of receptacle signal contacts, theplurality of receptacle signal contacts being disposed in a plurality ofparallel columns with each receptacle disposed to engage a pin shapedsignal contact; ii) a second plurality of shield plates, each shieldplate being disposed between adjacent columns of receptacle signalcontacts, wherein each of the second plurality of shield platesmechanically engages one of the first plurality of shield plates withcontact arms attached to one of the first or second plurality of shieldplates at two points.
 9. The electrical connector of claim 8 whereineach column of signal contacts has at least six signal contacts.
 10. Theelectrical connector of claim 8 additionally comprising a means forproviding a return current path for any given pin shaped signal contactdoes not cross any other pin shaped signal contact, wherein said meansincludes the first plurality of shield plates and the second pluralityof shield plates.
 11. The electrical connector of claim 8 wherein thetail portions of the signal contacts and the tail portions of the platesare press fit tails and the tail portions of the signal contacts are atright angles to the tail portions of the plates.
 12. The electricalconnector of claim 8 wherein a portion of the first plurality of plateshas a slot cut therein and the plate has a bend along a lineperpendicular to the slot, with the portion of the plate on one side ofthe bend forming a tail region and the portion of the plate on the otherside of the bend forming a shield region, with the tail region and theshield region being parallel and the tail portions being connected tothe tail region of the plate.
 13. The electrical connector of claim 8wherein the tail portions of the first plurality of plates are groundedin the backplane.
 14. An electrical connector with a first connectorpiece having a plurality of columns of signal contacts and a secondconnector piece having columns of signal contacts adapted to mate to thesignal contacts when the first connector piece and the second connectorpiece are mated, CHARACTERIZED IN THAT the connector furthercomprises:a) a first plurality of shield plates, each disposed betweenadjacent rows of signal contacts in the first connector piece; b) asecond plurality of shield plates, each disposed between adjacent rowsof signal contacts in the second connector piece; and c) a plurality ofcontacts on the first plurality or second plurality of shield plates,and wherein when the first connector piece and the second connectorpiece are mated, each of the first plurality of plates is parallel toand makes contact with one of the second plurality of plates at aplurality of points.
 15. The electrical connector of claim 14 whereinthe first connector piece comprises a pin header having a plurality ofrows of signal pins mounted in a shroud having two side walls with slotsformed therein and the first plurality of shield plates engage the slotson the side walls.
 16. The electrical connector of claim 15 wherein eachof the plurality of contacts on the first plurality or second pluralityof shield plates comprises an arm attached to the plate at two pointsand bent out of the plane of the plate.
 17. The electrical connector ofclaim 16 wherein there are a plurality of arms across the width of theplate.
 18. The electrical connector according to claim 14 wherein eachof the signal contacts has a tail (and each of the shield plates has aplurality of tails disposed between adjacent signal contact tails. 19.An electrical connector according to claim 14 wherein the secondconnector piece comprises a plurality of wafers aligned in parallel witheach of the second plurality of shields accessible from a side of one ofthe wafers, the wafers being positioned such that, when the firstconnector piece and the second connector piece are mated, the firstplurality of shields fit between adjacent wafers to make contact withone of the second plurality of shields.
 20. An electrical connectoraccording to any of claim 14 additionally comprising:a) a stiffener; b)a plurality of wafers, each of the wafers having a front face facing thefirst connector piece and a rear portion attached to the stiffener,thereby leaving slots between the front faces of adjacent wafers,wherein the first plurality of shield plates are inserted into theslots.
 21. An electrical connector according to claim 19 wherein each ofthe wafers includes one column of signal contacts secured in an housing.22. The electrical connector according to claim 14 wherein the signalcontacts in the second connector piece comprise receptacle contacts. 23.An electrical connector according to claim 14 wherein the firstconnector piece is attached to a backplane and the second connectorpiece is attached to a daughter card.